Exposure to trauma has a significant influence on developmental and mental health in young children. The proposed project is a renewal application designed to extend the findings of R01 MH079252-03 that successfully tested and modeled the relation between potential protective factors and mental health outcomes for a sample of 302 youth in foster care over three time points. The results indicated that constructs like child appraisal of events and coping or problem-solving style mediated the relation between maltreatment exposure and adjustment, specifically aggression. Moreover, the results indicated that cognitive systems like IQ operated as a moderator of the relation. Taken together, the results suggest the next line of research questions put forth in the proposed project. The project seeks to better illuminate the core components of appraisal (or threat perception) and problem-solving skills (or working memory skills) that accounted for adjustment in school-age youth by expanding the investigation to a younger age. In the proposed project, we will prospectively and longitudinally assess how dimensional components of trauma exposure (i.e., frequency, chronicity, and severity) influence the Negative Valence System (threat) and Cognitive Systems (working memory) to predict adjustment for early childhood-aged youth. The sample will be composed of 180 youth (and their parents and teachers) ages 3-5 at baseline, stratified by risk for trauma exposure making it possible to identify differential effects of trauma across a sample of youth who vary over time in their exposure to different levels of chronicity, frequency, and severity. The project will assess trauma as early as it can be reliably assessed across the spectrum of events commonly accepted as traumatic and provide a model test of the how the dimensions of those baseline traumas and new traumas over time impact emotion regulation and working memory. Moreover, the project will compare baseline emotion regulation and working memory functioning with post-trauma functioning in the smallest reasonable time frame so that the actual impact of the events on youth emotion regulation and working memory can be more reliably determined than ever before. The project will also extend the work by accounting for parental emotional response to the child in the exposure-outcome relation. The project is important and innovative in that it will include assessment of emotional regulation and working memory using state-of-the-art tools across a variety of modalities (physiological heart rate, observational measures, laboratory tasks, standardized measures, and self-report) to provide the clearest possible picture of the interaction between the constructs. Testing models of trauma dimensions over time and focusing on the core components of emotion regulation, working memory and parent-child interaction as mechanisms of how trauma confers risk to developmental health are rare and needed for the field to advance beyond long lists of the multifinality of responses youth demonstrate (both positive and detrimental) post-trauma exposure.